The present invention relates to damping devices and more particularly, to a hydraulic damping device for drawer, which buffers the reciprocating motion of the piston rod, allowing the piston rod to be moved out of the cylinder rapidly without much resistance and received in the inside of the cylinder slowly with much resistance. A shock-absorbing device is provided to buffer the impact when the piston rod is extended out of the cylinder.
U.S. Pat. No. 6,615,450B2 discloses an apparatus for the damping of impacts, preferably the impacts of furniture doors or drawers. According to this design, a compression spring is used to impart a damping resistance to the furniture drawer as the piston rod is moved to the inside of the cylinder. When the piston rod is extending out of the cylinder, the tube-section-like part of the compression spring is compressed to absorb shocks, lowering the noise level. However, because the compression spring has a certain length, it may cause an unsmooth movement of the piston rod.
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a hydraulic damper for drawer, which imparts a high damping resistance to the piston rod as the piston rod is moved toward the inside of the cylinder, smoothening the return stroke of the piston rod. It is another object of the present invention to provide a hydraulic damper for drawer, which allows the piston rod to be extended out of the cylinder at a high speed without much resistance and, which uses a shock absorbing device to absorb shocks and to buffer the impact when the piston rod is extended out of the cylinder, thereby lowering the noise level.
To achieve these and other objects of the present invention, the hydraulic damper comprises a cylinder holding a hydraulic fluid, a piston rod moving in and out of the cylinder and having a pin at one end inside the cylinder, a rigid valve block affixed to the inner end of the pin of the piston rod and having equiangularly spaced through holes, a retainer affixed to the outer end of the pin of the piston rod, a piston coupled to the pin of the piston rod and movable along the pin between the rigid valve block and the retainer and having a plurality of axially extending through holes, a number of the through holes of the piston being respectively aimed at the through holes of the rigid valve block for allowing the hydraulic fluid to pass through the piston in one direction at a high speed during outward stroke of the piston rod and to pass through the piston in the other direction at a low speed during inward stroke of the piston, and a shock absorber that buffers the impact of the rigid valve block when the piston rod is extended out of the cylinder.
Further, the piston has a plurality of spring strips. When the resisting force received by the piston is smaller than the spring power of the spring strips during return stroke of the piston, the spring strips immediately return to their former shape to suspend the raised portions thereof out of the rear side of the piston and to keep the piston apart from the rigid valve block for enabling the piston rod to be further extended out of the cylinder at a high speed with less resistance.